/*

Copyright (c) 2012, 2014-2020, Arvid Norberg
Copyright (c) 2016-2018, Alden Torres
Copyright (c) 2017, Andrei Kurushin
Copyright (c) 2017, Pavel Pimenov
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/config.hpp"
#include "libtorrent/string_util.hpp"
#include "libtorrent/random.hpp"
#include "libtorrent/error_code.hpp"
#include "libtorrent/parse_url.hpp"
#include "libtorrent/address.hpp"
#include "libtorrent/assert.hpp"

#include <cstdlib> // for malloc
#include <cstring> // for strlen
#include <algorithm> // for search

namespace libtorrent {

	// We need well defined results that don't depend on locale
	std::array<char, 4 + std::numeric_limits<std::int64_t>::digits10>
		to_string(std::int64_t const n)
	{
		std::array<char, 4 + std::numeric_limits<std::int64_t>::digits10> ret;
		char *p = &ret.back();
		*p = '\0';
		// we want "un" to be the absolute value
		// since the absolute of INT64_MIN cannot be represented by a signed
		// int64, we calculate the abs in unsigned space
		std::uint64_t un = n < 0
			? std::numeric_limits<std::uint64_t>::max() - std::uint64_t(n) + 1
			: std::uint64_t(n);
		do {
			*--p = '0' + un % 10;
			un /= 10;
		} while (un);
		if (n < 0) *--p = '-';
		std::memmove(ret.data(), p, std::size_t(&ret.back() - p + 1));
		return ret;
	}

	bool is_alpha(char c)
	{
		return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
	}

	bool is_print(char c)
	{
		return c >= 32 && c < 127;
	}

	bool is_space(char c)
	{
		return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v';
	}

	char to_lower(char c)
	{
		return (c >= 'A' && c <= 'Z') ? c - 'A' + 'a' : c;
	}

	bool string_begins_no_case(char const* s1, char const* s2)
	{
		TORRENT_ASSERT(s1 != nullptr);
		TORRENT_ASSERT(s2 != nullptr);

		while (*s1 != 0)
		{
			if (to_lower(*s1) != to_lower(*s2)) return false;
			++s1;
			++s2;
		}
		return true;
	}

	bool string_equal_no_case(string_view s1, string_view s2)
	{
		if (s1.size() != s2.size()) return false;
		return std::equal(s1.begin(), s1.end(), s2.begin()
			, [] (char const c1, char const c2)
			{ return to_lower(c1) == to_lower(c2); });
	}

	// generate a url-safe random string
	void url_random(span<char> dest)
	{
		// http-accepted characters:
		// excluding ', since some buggy trackers don't support that
		static char const printable[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
			"abcdefghijklmnopqrstuvwxyz-_.!~*()";

		// the random number
		std::generate(dest.begin(), dest.end()
			, []{ return printable[random(sizeof(printable) - 2)]; });
	}

	bool string_ends_with(string_view s1, string_view s2)
	{
		return s1.size() >= s2.size() && std::equal(s2.rbegin(), s2.rend(), s1.rbegin());
	}

	int search(span<char const> src, span<char const> target)
	{
		TORRENT_ASSERT(!src.empty());
		TORRENT_ASSERT(!target.empty());
		TORRENT_ASSERT(target.size() >= src.size());
		TORRENT_ASSERT(target.size() < std::numeric_limits<int>::max());

		auto const it = std::search(target.begin(), target.end(), src.begin(), src.end());

		// no complete sync
		if (it == target.end()) return -1;
		return static_cast<int>(it - target.begin());
	}

	char* allocate_string_copy(string_view str)
	{
		if (str.empty()) return nullptr;
		auto* tmp = new char[str.size() + 1];
		std::copy(str.data(), str.data() + str.size(), tmp);
		tmp[str.size()] = '\0';
		return tmp;
	}

#if TORRENT_ABI_VERSION == 1 \
	|| !defined TORRENT_DISABLE_LOGGING
	std::string print_listen_interfaces(std::vector<listen_interface_t> const& in)
	{
		std::string ret;
		for (auto const& i : in)
		{
			if (!ret.empty()) ret += ',';

			error_code ec;
			make_address_v6(i.device, ec);
			if (!ec)
			{
				// IPv6 addresses must be wrapped in square brackets
				ret += '[';
				ret += i.device;
				ret += ']';
			}
			else
			{
				ret += i.device;
			}
			ret += ':';
			ret += to_string(i.port).data();
			if (i.ssl) ret += 's';
			if (i.local) ret += 'l';
		}

		return ret;
	}
#endif

	string_view strip_string(string_view in)
	{
		while (!in.empty() && is_space(in.front()))
			in.remove_prefix(1);

		while (!in.empty() && is_space(in.back()))
			in.remove_suffix(1);
		return in;
	}

	// this parses the string that's used as the listen_interfaces setting.
	// it is a comma-separated list of IP or device names with ports. For
	// example: "eth0:6881,eth1:6881" or "127.0.0.1:6881"
	std::vector<listen_interface_t> parse_listen_interfaces(std::string const& in
		, std::vector<std::string>& err)
	{
		std::vector<listen_interface_t> out;

		string_view rest = in;
		while (!rest.empty())
		{
			string_view element;
			std::tie(element, rest) = split_string_quotes(rest, ',');

			element = strip_string(element);
			if (element.size() > 1 && element.front() == '"' && element.back() == '"')
				element = element.substr(1, element.size() - 2);
			if (element.empty()) continue;

			listen_interface_t iface;
			iface.ssl = false;
			iface.local = false;

			string_view port;
			if (element.front() == '[')
			{
				auto const pos = find_first_of(element, ']', 0);
				if (pos == string_view::npos
					|| pos+1 >= element.size()
					|| element[pos+1] != ':')
				{
					err.emplace_back(element);
					continue;
				}

				iface.device = strip_string(element.substr(1, pos - 1)).to_string();

				port = strip_string(element.substr(pos + 2));
			}
			else
			{
				// consume device name
				auto const pos = find_first_of(element, ':', 0);
				iface.device = strip_string(element.substr(0, pos)).to_string();
				if (pos == string_view::npos)
				{
					err.emplace_back(element);
					continue;
				}
				port = strip_string(element.substr(pos + 1));
			}

			// consume port
			std::string port_str;
			for (std::size_t i = 0; i < port.size() && is_digit(port[i]); ++i)
				port_str += port[i];

			if (port_str.empty() || port_str.size() > 5)
			{
				err.emplace_back(element);
				continue;
			}

			iface.port = std::atoi(port_str.c_str());
			if (iface.port < 0 || iface.port > 65535)
			{
				err.emplace_back(element);
				continue;
			}

			port.remove_prefix(port_str.size());
			port = strip_string(port);

			// consume potential SSL 's'
			for (auto const c : port)
			{
				switch (c)
				{
					case 's': iface.ssl = true; break;
					case 'l': iface.local = true; break;
				}
			}

			TORRENT_ASSERT(iface.port >= 0);
			out.emplace_back(iface);
		}

		return out;
	}

	// this parses the string that's used as the dht_bootstrap setting.
	// it is a comma-separated list of IP or hostnames with ports. For
	// example: "router.bittorrent.com:6881,router.utorrent.com:6881" or "127.0.0.1:6881"
	void parse_comma_separated_string_port(std::string const& in
		, std::vector<std::pair<std::string, int>>& out)
	{
		out.clear();

		std::string::size_type start = 0;
		std::string::size_type end = 0;

		while (start < in.size())
		{
			// skip leading spaces
			while (start < in.size()
				&& is_space(in[start]))
				++start;

			end = in.find_first_of(',', start);
			if (end == std::string::npos) end = in.size();

			std::string::size_type colon = in.find_last_of(':', end);

			if (colon != std::string::npos && colon > start)
			{
				int port = std::atoi(in.substr(colon + 1, end - colon - 1).c_str());

				// skip trailing spaces
				std::string::size_type soft_end = colon;
				while (soft_end > start
					&& is_space(in[soft_end-1]))
					--soft_end;

				// in case this is an IPv6 address, strip off the square brackets
				// to make it more easily parseable into an ip::address
				if (in[start] == '[') ++start;
				if (soft_end > start && in[soft_end-1] == ']') --soft_end;

				out.emplace_back(in.substr(start, soft_end - start), port);
			}

			start = end + 1;
		}
	}

	void parse_comma_separated_string(std::string const& in, std::vector<std::string>& out)
	{
		out.clear();

		std::string::size_type start = 0;
		std::string::size_type end = 0;

		while (start < in.size())
		{
			// skip leading spaces
			while (start < in.size()
				&& is_space(in[start]))
				++start;

			end = in.find_first_of(',', start);
			if (end == std::string::npos) end = in.size();

			// skip trailing spaces
			std::string::size_type soft_end = end;
			while (soft_end > start
				&& is_space(in[soft_end - 1]))
				--soft_end;

			out.push_back(in.substr(start, soft_end - start));
			start = end + 1;
		}
	}

	std::pair<string_view, string_view> split_string(string_view last, char const sep)
	{
		auto const pos = last.find(sep);
		if (pos == string_view::npos) return {last, {}};
		else return {last.substr(0, pos), last.substr(pos + 1)};
	}

	std::pair<string_view, string_view> split_string_quotes(string_view last, char const sep)
	{
		if (last.empty()) return {{}, {}};

		std::size_t pos = 0;
		if (last[0] == '"' && sep != '"')
		{
			for (auto const c : last.substr(1))
			{
				++pos;
				if (c == '"') break;
			}
		}
		std::size_t found_sep = 0;
		for (char const c : last.substr(pos))
		{
			if (c == sep)
			{
				found_sep = 1;
				break;
			}
			++pos;
		}
		return {last.substr(0, pos), last.substr(pos + found_sep)};
	}

	void ltrim(std::string& s)
	{
		while (!s.empty() && is_space(s.front()))
			s.erase(s.begin());
	}

	std::string format_host_for_connect(std::string host, unsigned short const port)
	{
		// Handle edge case: if no port specified, return host as-is
		if (port == 0) return host;

		// Already bracketed IPv6 literal
		if (!host.empty() && host.front() == '[' && host.back() == ']')
		{
			host += ":";
			host += to_string(port).data();
			return host;
		}

		// Contains colons (unbracketed IPv6) - need to bracket
		if (host.find(':') != string_view::npos)
		{
			host = "[" + host;
			host += "]:";
			host += to_string(port).data();
			return host;
		}

		// Regular hostname or IPv4
		host += ":";
		host += to_string(port).data();
		return host;
	}

#if TORRENT_USE_I2P

	bool is_i2p_url(std::string const& url)
	{
		using std::ignore;
		std::string hostname;
		error_code ec;
		std::tie(ignore, ignore, hostname, ignore, ignore)
			= parse_url_components(url, ec);
		return string_ends_with(hostname, ".i2p");
	}

#endif
}
